MERCURY in FISH What Fish Are Safe?
Total Page:16
File Type:pdf, Size:1020Kb
UCSC SIGMA XI LECTURE 2009 Tuesday April 28 -- 8 pm Engineering Lecture Hall, UCSC MERCURY IN FISH What Fish Are Safe? NED GROTH Senior Scientist, Consumers Union (retired), consultant to UN Food and Agriculture Organization and World Health Organization The speaker, Dr. Ned Groth III, has recently authored a major study on methyl mercury in fish. This talk will dis- cuss cases of people who suffered from methylmercury poisoning after eating widely consumed fish. Methylmer- cury is very toxic to the nervous system. Some kinds of fish have much more methylmercury than others, and some people are much more sensitive to mercury than others. The talk concludes with advice on which fish are safe, which fish should be consumed in small quantities, and which fish should be eaten rarely if ever. It should be of interest to everyone who eats fish or is interested in environmental issues. From 1979 until his retirement in 2004, Groth was a scientific expert at Consumers Union, publisher of Consumer Reports magazine. He is the author or coauthor of many books and studies, and he has also served on the Food Forum of the National Academy of Sciences and on expert committees for the World Health Organization and the UN Food and Agriculture Organization. This lecture is sponsored by UCSC Chapter of Sigma Xi (the Scientific Research Society), and by the UCSC Departments of Physics and of Microbiology and Environmental Toxicology (ETOX) . MethylmercuryMethylmercury PoisoningPoisoning inin High-EndHigh-End FishFish Consumers:Consumers: AA RiskRisk CommunicationCommunication ChallengeChallenge Edward Groth III, PhD Groth Consulting Services Pelham, NY 10803 USA April, 2009 TopicsTopics toto bebe covered:covered: Background & context Mercury in US fish and seafood Summary of 24 case histories Is it really methylmercury poisoning? Dose-response issues Fish involved in these cases How prevalent a problem? Research needs Risk communication aspects ContextContext Americans are eating more fish, which benefits public health significantly, overall But it also increases the likelihood of exposure to methylmercury, from eating fish Risk is greater for people who eat a lot of fish The type(s) of fish consumed also matter Methylmercury exposure in general and extreme high-end exposure are each likely to increase if more Americans eat more fish ConventionalConventional HgHg Wisdom:Wisdom: CriticalCritical effecteffect == developmentaldevelopmental neurotoxicityneurotoxicity PopulationsPopulations atat riskrisk == fetusesfetuses (i.e.(i.e. womenwomen ofof childbearingchildbearing age)age) andand youngyoung childrenchildren NoNo appreciableappreciable riskrisk toto otherother populationspopulations BenefitsBenefits (lower(lower risksrisks ofof CHDCHD && stroke)stroke) farfar outweighoutweigh HgHg risksrisks forfor generalgeneral populationpopulation ThisThis perspectiveperspective isis reflectedreflected asas recentlyrecently asas inin thethe 20062006 NAS/IOMNAS/IOM reportreport onon benefitsbenefits andand risksrisks ofof fishfish && seafoodseafood consumptionconsumption BasisBasis forfor C.W.:C.W.: EpidemiologyEpidemiology fromfrom incidentsincidents inin JapanJapan andand Iraq,Iraq, mostmost studiesstudies 30-4030-40 yearsyears agoago FoundFound clear-cutclear-cut neurotoxicneurotoxic effectseffects inin adultsadults onlyonly atat highhigh dosesdoses (blood(blood HgHg >> ~200~200 ppb)ppb) SomeSome effectseffects inin childrenchildren @@ >> 5050 ppbppb AmountsAmounts ofof MeHgMeHg fromfrom fishfish inin ““normalnormal dietdiet”” believedbelieved toto bebe belowbelow thethe levellevel ofof concern,concern, exceptexcept forfor potentialpotential forfor fetalfetal exposureexposure KeyKey questions:questions: DoDo wewe needneed toto revisitrevisit andand updateupdate thisthis riskrisk assessment?assessment? IfIf so,so, howhow mightmight wewe approachapproach thatthat task?task? WhatWhat aboutabout ““abnormalabnormal”” (high-fish)(high-fish) diets?diets? OnOn whatwhat issuesissues dodo wewe needneed betterbetter data?data? GivenGiven whatwhat wewe knowknow andand dondon’’tt know,know, whatwhat adviceadvice shouldshould wewe givegive consumers?consumers? AA FewFew BasicBasic PrinciplesPrinciples ofof EnvironmentalEnvironmental HealthHealth RiskRisk isis aa ContinuumContinuum SensitivitySensitivity toto toxictoxic effectseffects variesvaries alongalong aa distributiondistribution Number of individuals affected Dose SensitiveSensitive subpopulationsubpopulation Number affected Dose FishFish consumptionconsumption andand methylmercurymethylmercury exposureexposure FishFish consumptionconsumption Long-termLong-term trendtrend ofof increasingincreasing perper capitacapita consumptionconsumption inin USUS RecentRecent yearsyears at/nearat/near all-timeall-time highhigh PatternsPatterns ofof consumptionconsumption alsoalso changingchanging MoreMore freshfresh andand frozenfrozen steakssteaks andand filletsfillets MoreMore (mostly(mostly imported)imported) shrimpshrimp LessLess cannedcanned andand breaded/processedbreaded/processed fishfish USUS PerPer capitacapita fishfish consumption,consumption, pounds/year,pounds/year, 1990-20061990-2006 (NMFS)(NMFS) 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 ConsumptionConsumption ofof selectedselected items,items, pounds/person/year,pounds/person/year, 1990-20061990-2006 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 PerPer capitacapita consumption,consumption, cannedcanned fish,fish, pounds/year,pounds/year, 1990-20061990-2006 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 TopTop 1010 SeafoodsSeafoods,, 2005-20072005-2007 US consumption in pounds per capita per year (NFI) Rank 2005 2006 2007 . Species Lbs Species Lbs Species Lbs 1 Shrimp 4.10 Shrimp 4.40 Shrimp 4.10 2 Tuna, can 3.10 Tuna, can 2.90 Tuna, can 2.70 3 Salmon 2.43 Salmon 2.03 Salmon 2.36 4 Pollock 1.47 Pollock 1.64 Pollock 1.73 5 Catfish 1.03 Tilapia 1.00 Tilapia 1.14 6 Tilapia 0.85 Catfish 0.97 Catfish 0.88 7 Crab 0.64 Crab 0.66 Crab 0.68 8 Cod 0.57 Cod 0.51 Cod 0.47 9 Clams 0.44 Clams 0.44 Clams 0.45 10 Flatfish 0.37 Scallops 0.31 Flatfish 0.32 Total, Top 10 15.0 14.9 14.8 WhereWhere’’ss thethe mercury?mercury? AmongAmong popularpopular fishfish andand seafoodseafood choices,choices, howhow muchmuch doesdoes eacheach varietyvariety contributecontribute toto potentialpotential methylmercurymethylmercury exposure?exposure? WhichWhich fishfish areare likelylikely toto contributecontribute mostmost toto methylmercurymethylmercury intake,intake, amongamong peoplepeople whowho eateat aa greatgreat dealdeal ofof fish?fish? MethylmercuryMethylmercury Exposure:Exposure: SourceSource StrengthsStrengths ContributionsContributions ofof differentdifferent fishfish andand seafoodseafood itemsitems toto totaltotal amountamount ofof mercurymercury inin thethe USUS fish/seafoodfish/seafood supply,supply, calculatedcalculated using:using: A:A: 20062006 USUS marketmarket datadata fromfrom NMFSNMFS B:B: MercuryMercury contentcontent fromfrom FDAFDA databasedatabase HgHg InputInput == (%(% ofof market)market) xx (Hg(Hg ppm)ppm) RelativeRelative HgHg ContributionsContributions Hg inputs calculated for 51 types of fish and shellfish for which there are both NMFS market data and FDA Hg data Results are not precise indicators of exposure, but provide relative comparisons Results can be ranked and compared various ways (e.g., percent of total Hg) AA KeyKey Fact:Fact: The weighted average methylmercury concentration in the US seafood supply is 0.086 ppm Color-codingColor-coding fishfish forfor methylmercurymethylmercury contentcontent GREEN = very low = < 0.043 ppm BLUE = below average = 0.044 - 0.086 ppm BLACK = above average = 0.087 - 0.172 ppm ORANGE = moderately high = 0.173 - 0.344 ppm RED = high = 0.345 - 0.688 ppm VIOLET = very high = > 0.688 ppm Note: Different breakpoints than FDA has used TopTop 1010 SeafoodsSeafoods,, 2005-20072005-2007 US consumption in pounds per capita per year (NFI) Rank 2005 2006 2007 . Species Lbs Species Lbs Species Lbs 1 Shrimp 4.10 Shrimp 4.40 Shrimp 4.10 2 Tuna, can 3.10 Tuna, can 2.90 Tuna, can 2.70 3 Salmon 2.43 Salmon 2.03 Salmon 2.36 4 Pollock 1.47 Pollock 1.64 Pollock 1.73 5 Catfish 1.03 Tilapia 1.00 Tilapia 1.14 6 Tilapia 0.85 Catfish 0.97 Catfish 0.88 7 Crab 0.64 Crab 0.66 Crab 0.68 8 Cod 0.57 Cod 0.51 Cod 0.47 9 Clams 0.44 Clams 0.44 Clams 0.45 10 Flatfish 0.37 Scallops 0.31 Flatfish 0.32 Total, Top 10 15.0 14.9 14.8 TopTop 1010 HgHg SourcesSources Market Fish Share (%) ppm Hg Percent Hg Tuna, all types 16.44 next slide 37.37 Haddock & Hake 4.86 0.170 9.73 Swordfish 0.44 0.976 5.06 Catfish 5.71 0.068 4.66 Cod 3.36 0.115 4.55 American lobster 1.22 0.310 4.46 Pollock 7.32 0.049 4.23 Shrimp 22.21 0.012 3.14 Salmon 6.83 0.028 2.25 Sea Bass 0.51 0.301 1.81 Total 77.26 Tuna,Tuna, byby typetype Type Market % ppm Hg % Hg Canned albacore 3.81 0.353 15.85 Canned light 11.41 0.118 15.86 Fresh/Frozen 1.22 0.384 5.66 Totals 16.44 37.37 (Insufficient supply data to specify contributions by tuna type to fresh/frozen category, e.g., bluefin, albacore, bigeye, etc.) CommentsComments onon TopTop 1010 Swordfish is the only Violet (very high Hg) fish among the Top 10 sources Two Green (very low Hg) and two Blue (below average Hg) items unlikely to be hazards; in Top 10 due to huge volume consumed Two Black and two Orange items could lead to excessive exposure if eaten frequently Tuna (two Red, one Black) is overwhelmingly the largest source Top 10 account for more than _ of all mercury OtherOther